i don't know much about this subject, but I don't recall any explicit example in the bible of anyone in the faith physically beating his/her own body, unless it was a simply beating of the chest out of anguish.
does anyone know of a biblical example?
No. And certainly not for the purpose of "getting closer to Jesus", as some Opus Dei practitioners claim. The point is, theologically, that Jesus took the stripes that were meant for us and we cannot do anything (including suffer) to merit God's favor. He has already done that for us. One of my Opus Dei acquaintances wears a belt with small, jagged edges on it so he can be uncomfortable and even cut throughout the day. He says it reminds him of the pain Christ endured for him...and, while I respect his sincerity and his desire to honor Jesus...I see no Scriptural support for his activity and, in fact, it could lead SOME practitioners to errantly believe they are paying for their sins at least in part. If so, Jesus' final declaration on the cross that, "It is finished" was in error.
St. Paul did say, "I buffet my body"...but then we get into the whole problem of taking everything in Scripture literally. Contextually, it seems clear to me that Paul was talking about controlling his urges, denying his selfish desires in favor of service to others and obedience to Christ. I don't see anything there indicating he was beating himself.
I do draw a distinction between fasting and other forms of self denial and actual self-flagellation. And maybe I am putting too fine a point on it. But even fasting is supposed to be done with a view toward common sense and self preservation (not fasting if you are physically or medically unable, etc.) Fasting is supposed to cause one to recognize the lack of something and, in lacking, to realize the sufficiency of Christ. I don't see how whipping yourself does that in anyway.
There is so much I respected about the previous pontiff and I mean no disrespect to my brother and sister Roman Catholics. Most of the Catholics I know are far better Christians than me and very, very few are members of Opus Dei...which strikes me as a bizarre, almost cult-like movement. But again...I speak from a certainly level of ignorance and will defer to Chris or others with a greater experience with the RCC.